High-frequency oven



Sept. 29, 1964 P. s. BRITTON 3,151,230

HIGH-FREQUENCY OVEN Filed July 12, 1960 United States Patent The invention relates to a high-frequency oven, in particular for high-frequency heating by means of ultrahigh-frequency oscillations, for example in the decimeter or centimeter range, provided with a closed heating chamber havingan entry port and an exit port for the passage of a conveyor belt conveying the articles to be heated through the heating chamben'the entry port and the exit port being each provided with a channel extending in the direction of the conveyor and enclosing it outside the heating chamber.

In such high-frequency ovens, stray radiation escaping from the oven provides diificulty, for the ultra highfrequency oscillations set up in the heating. chamber may pass through the entry andexit ports and the associated channels. It is known to reduce this leakage of radiation by making the length of these channels equal to a quarter wavelength or an odd number of quarter wavelengths of the ultra high-frequency oscillations so that the channels act as rejection filters for these oscillations.

The present invention provides a different design of a high-frequency oven of. the above-mentioned type, in which the stray radiation escaping from the high-frequency oven is substantially suppressed while furthermore more even heating is obtained in the heating chamber.

The oven in accordance with the invention is characterized in that a number of evenly spaced sealing members of conductive material are secured to the conveyor belt at right angles thereto, which, when the assembly is passed through the channels, form in conjunction with the inner walls of these channels an electric seal for the highfrequency oscillations, the length of the channels being at least equal to the spacing of these sealing members.

The invention and its advantages will now be described with reference to the figures.

FIG. l'shows a high-frequency oven in accordance with the invention.

FIG. 2 is a cross-sectional view of a part of the highfrequency oven, while FIG. 3 is a cross-sectional view of a modified embodi-- ment.

The high-frequency oven in accordance with the invention shown in FIG. 1 comprises a heating chamber 1 to which through a waveguide system 2 ultra high-frequency oscillations are supplied from an ultrahigh-frequency generator, for example a magnetron generator (not shown). The heating chamber 1 is provided with a rectangular entry port 3, a rectangular exit port 4 and rectangular channels 5 and 9 connected to these ports, a conveyor belt 6 passing through the channels 5, 9 for moving the articles to be heated through the closed heating chamber.

In order effectively to suppress any stray radiation escaping through the channels 5, 9 a number of evenly spaced sealing members 7 made of conductive material, for example copper or brass, are secured to the conveyor belt 6 in a direction at right angles to this belt 6 so as to form on passage through the channels 5, 9 in conjunction with the inner Walls of these channels 5, 9 an electric seal for the ultra high-frequency oscillations, the length of the channels 5, 9 being at least equal to the spacing of these 3,151,230 Patented Sept. 29, 1964 sealing members 7. The sealing members 7 may be secured to the conveyor by rivets or by means of an adhesive while the belt may be made of glass fibres or some other material having a low loss factor.

In the embodiment shown, the sealing members are metal plates of rectangular shape, the ends of these sealing members 7 adjacent the inner walls of the channels 5 and 9 being bent over in a direction parallel to the inner Walls of these channels 5 and 9 in order to ensure tight capacitive coupling between these sealing members 7 and the channels 5 and 9, so that a cross-section of such a member is shaped in the form of an I or U. For the ultra high-frequency oscillations these sealing members 7 substantially behave as metallic seals so that any stray radiation from the high-frequency oven is substantially suppressed.

FIG. 2 is a cross-sectional view of the high-frequency oven shown in FIG. 1, articles 8 to be heated being dis posed between sealing members 7 of I-shaped crosssection.

When in this oven the conveyor belt 6 is passed through the heating chamber, the channels 5 and 9 are always effectively sealed for the fact that the length of these channels 5 and 9 is made at least equal to the spacing between two sealing members 7 ensures that always at least one of these sealing members 7 is located in each channel 5 and 9 so that these channels are effectively sealed.

The sealing members 7 moving together with the conveyor belt 6 to the heating chamber 1 not only provide an effective seal of the channels 5 and 9, but also prevent a stationary standing field distribution from occurring in the heating chamber 1 so that a more uniform field distribution. is obtained without separate means, such as slowly rotating metal vanes or rotating dipoles for supplying the ultra-high frequency oscillations to the heating chamber being required. Each metal sealing member 7 by its movement disturbs a stationary standing field distribution in the heating chamber 1 and this effect may be enhanced by the provision on the conveyor belt of uniformly spaced further means, for example metal plates, rods or the like, which further improve the uniformity of the field distribution.

Thus, the use of the simple steps in accordance with the invention ensures not only elfective sealing against stray radiation but also more even heating.

In designing high-frequency ovens in accordance with the invention, allowance must be made for the size of the articles to be heated, for example, if these articles 8 are large, the spacing between successive sealing members 7 and hence the length of the channels 5 and 9 must also be large, as is shown in FIG. 3.

What is claimed is:

1. A high frequency oven heated by ultra high frequency oscillations comprising a chamber having a pair of channels extending therefrom at opposite sides of said chamber forming an entry and exit port respectively, a conveyor belt for conveying the articles to be heated through said chamber, a plurality of spaced sealing members secured to said conveyor and constituted of conductive material, said sealing members extending perpendicular to the length of said conveyor belt, the shape of said members being such as to correspond to the inner configurations of said channels thereby forming an elec tric seal for the ultra high frequency oscillations in the oven, the length of each of said channels being at least equal to the spacing between adjacent sealing members.

single conveyor belt for conveying the articles to be heated through said chamber, a plurality of spaced sealing members secured to said conveyor and constituted of conductive material, said sealing members extending perpendicular to the length of said conveyor belt and having end portions bent over to a position at right angles to said sealing members and parallel to said conveyor belt, the shape of said members being such as to corre spond to the inner configurations of said channels thereby forming an electric seal for the ultra high frequency oscillations in the oven, the length of each of said channels being at least equal to the spacing between adjacent sealing members.

3. A high frequency oven heated by ultra high frequency oscillations as claimed in claim 1 wherein said sealing members are I-shaped and are so arranged on said conveyor belt as to influence the field distribution of heat- 5 ing in said chamber.

References Cited in the file of this patent UNITED STATES PATENTS 10 2,353,362 Rudd July 11, 1944 2,467,230 Revercomb et a1 Apr. 12, 1949 2,868,939 Pound Jan. 13, 1959 

1. A HIGH FREQUENCY OVEN HEATED BY ULTRA HIGH FREQUENCY OSCILLATIONS COMPRISING A CHAMBER HAVING A PAIR OF CHANNELS EXTENDING THEREFROM AT OPPOSITE SIDES OF SAID CHAMBER FORMING AN ENTRY AND EXIT PORT RESPECTIVELY, A CONVEYOR BELT FOR CONVEYING THE ARTICLES TO BE HEATED THROUGH SAID CHAMBER, A PLURALITY OF SPACED SEALING MEMBERS SECURED TO SAID CONVEYOR AND CONSTITUTED OF CONDUCTIVE MATERIAL, SAID SEALING MEMBERS EXTENDING PERPENDICULAR TO THE LENGTH OF SAID CONVEYOR BELT, THE SHAPE OF SAID MEMBERS BEING SUCH AS TO CORRESPOND TO THE INNER CONFIGURATIONS OF SAID CHANNELS THEREBY FORMING AN ELECTRIC SEAL FOR THE ULTRA HIGH FREQUENCY OSCILLATIONS IN THE OVEN, THE LENGTH OF EACH OF SAID CHANNELS BEING AT LEAST EQUAL TO THE SPACING BETWEEN ADJACENT SEALING MEMBERS. 